1. Field of the Invention
The invention relates to a cosmetic composition of improved physical stability and skin performance properties
2. The Related Art
Hosts of commercial emollient creams and lotions claim alleviation of the signs and symptoms of dry skin. Application of these products is intended to return skin to a normal condition by moisturizing and reducing evaporation of water from the skin. Most dry skin products are oil-in-water anionic or non-ionic emulsions. As a result, these products wash off with water and then must be re-applied.
Cationic emulsions occupy a much smaller market segment, but can possess certain skin feel advantages. In U.S. Pat. No. 4,389,418 (Burton) there is disclosed a water-out emulsion containing petrolatum or a mineral oil to moisturize the skin, a quaternary ammonium emulsifier, a fatty alcohol and a fatty ester emollient. Greaseless skin conditioning compositions based upon cationic polymers have also been reported in U.S. Pat. No. 4,438,095 (Grollier). Among the polymers disclosed are polyamines, polyaminoamides or quaternary polyammonium compounds. Emulsions are formed wherein the aqueous phase contains the cationic polymer and there are no detergent or foaming agents present.
Diquaternary nitrogen compounds have been reported in U.S. Pat. No. 4,886,890 (Chaudhuri et al) as useful in skin lotions and shampoos. These compositions may be formulated with a variety of detergents, such as sodium laureth-4 phosphate. Personal care products incorporating cationic polysaccharides have been described in U.S. Pat. No. 4,663,159 (Brode et al). Emulsifiers in the form of phosphate quaternary compounds have been disclosed in U.S Pat. No. 4,209,449 and U.S. Pat. No. 4,503,002, each to Mayhew et al. These emulsifiers were said to be well tolerated by human tissue, exhibiting low irritation, and were stated to be suitable for use in cosmetics.
Skin moisture retention has been significantly increased by utilizing many of the cationic compounds mentioned in the above patents. Nonetheless, there remains considerable need for improvement for moisture retention. There are also the further problems of improving mildness and of providing stability against phase separation during freeze-thaw cycles.
Accordingly, it is an object of the present invention to provide a cosmetic composition of improved skin moisture retention.
Another object of the present invention is to provide a cosmetic composition having a relatively low human tissue irritancy.
A further object of the present invention is to provide a cosmetic composition in aqueous emulsion form whose phases resist separation even under extended freeze-thaw cycling.
These and other objects of the present invention will more readily become apparent from the description and examples which follow.